The Stickleback: Evidence of evolution?

Published: 8 September 2009 (GMT+10)

Photo by sam2cents, flickr.com
The stickleback—an evolutionary ‘superstar’? Charles Darwin did
not mention the stickleback in his 1859 On the Origin of Species. In his
subsequent writings, Darwin briefly referred to the stickleback when he was struggling
with the question of how animals select mates, and the male stickleback’s
devoted care of the young. But today, the stickleback has become an ‘icon’
of evolution.

“One of the most compelling case studies of evolution” is how one leading
biologist labelled the stickleback fish (Gasterosteus spp.).1 A Science journal writer termed it a “star”
of evolutionary research.2
Another science reporter went even further, dubbing it as a “superstar
of evolutionary science”, adding that “Sticklebacks are so central to
the new wave of evolutionary research that they may well eclipse Darwin’s
finches in importance and earn the honorary title of ‘Darwin’s finches’.”3

Not to be outdone in this anniversary
“Year of Darwin”, Nature journal has honoured the stickleback
as one of “15 Evolutionary Gems”.4

But on what evidence do they base these grandiose claims?

Differences between saltwater and freshwater sticklebacks

Threespine sticklebacks can be found in oceans and coastal rivers and streams in
north America, Japan and northern Asia and Europe.

The oceangoing sticklebacks spend most of their adult life in the sea, returning
to freshwater to breed.5

The saltwater form is morphologically similar all around the Northern Hemisphere,
with adults typically between 6–10 cm (2–4 in.) in length, with long
dorsal and pelvic spines. Lacking scales, their bodies are covered by as many as
36 armour plates covering their sides6
—believed to protect sticklebacks against predatory fish. Certainly the spines
seem to serve that purpose, because when a larger fish tries to eat a marine stickleback,
the stickleback defends itself by extending the spines on its back and pelvis.

In contrast to the saltwater form, freshwater populations are extremely morphologically
diverse, with great variation between sticklebacks from different streams or lakes.7 They also have generally shorter
dorsal and pelvic spines and substantially fewer armour plates (normally 12 or less)
than their marine counterparts. In fact, many freshwater sticklebacks have no pelvic
spines or armour plates at all.

These differences between saltwater and freshwater forms of the stickleback are
paraded as evidence of evolution, i.e. the marine form “evolved” into
the freshwater form over evolutionary timescales:

“Sticklebacks were once a solely saltwater species that migrated from the
sea to streams and lakes to breed; as the glaciers retreated up to 22,000 years
ago, some settled in lakes. Although they evolved to look very different from their
ancestors, they often came to resemble their counterparts who were evolving in a
similar way in lakes that are geographically distant.”2,8

It is certainly not unreasonable to conclude that the freshwater stickleback is
descended from the saltwater form. After all, ocean-going sticklebacks migrate up
streams to inland freshwater lakes to spawn, both freshwater and saltwater populations
can interbreed, and, as we shall see, recent observations certainly support this.
But are the changes in stickleback morphology really evolutionary? Is the stickleback’s
“disappearing armour” truly evidence for the capacity of fish
to have gradually evolved into philosophers over supposed hundreds of millions
of years?

Somewhat ironically, thanks to evolutionary scientists’ eagerly directing
their attention to the stickleback and various freshwater lakes as “natural
laboratories for evolutionary studies”, these questions have been answered—by
evolutionists themselves. As we shall see, stickleback changes have been acknowledged
as not only providing no support for molecules-to-man evolution, but have also upset
the “slow-and-gradual” long-age evolutionary mindset.

Recolonization of a freshwater lake by ocean sticklebacks, and subsequent adaptation

Loberg Lake is a small (~4.5 hectares) lake in Southern Alaska. In 1982 the Alaska
Department of Fish and Game poisoned all the fish in Loberg Lake to improve the
lake for recreational fishing (i.e. as preparation for restocking the lake with
salmon and trout). Thus Loberg’s native freshwater stickleback population
was exterminated.

However, eight years later, researchers sampling Lake Loberg found that the sticklebacks
were back. But these new sticklebacks were strikingly different from the pre-1982
population, as they were heavily armoured, like ocean-going sticklebacks. The researchers
surmised, quite reasonably, that saltwater sticklebacks had made their way upstream
from Cook Inlet and colonized Lake Loberg sometime between 1983 and 1989.9

In the years since 1990, however, annual sampling of the lake’s sticklebacks
revealed a progressive reduction in body armour. In 1990, fully-plated sticklebacks
made up 96% of the population, but just three years later, only 39% had the full
suite of bony body plates.10
Individuals with only the front plates first appeared in 1991, but by 2001 their
numbers had increased to 75%.

Thus after just a few generations (sticklebacks take 1–3 years to reach maturity),
the sticklebacks in Lake Loberg increasingly resembled the pre-1982 native stickleback
population, and their freshwater counterparts in other Alaskan lakes and streams.
So what had driven this rapid reduction of armour plating and pelvic spines?

Natural selection at work

Freshwater and saltwater sticklebacks can interbreed

Looking past the hype of researchers’ claims that this is “rapid evolution”,9
it is in fact a classic example of “strong natural selection acting on variation
that was carried by the anadromous11
fish that colonized the lake”.9 Notice that natural selection acted
on existing variation in the colonizing stickleback population. In other
words, the so-called “rapid evolution” did not result in the addition
of any new features but rather the reduction or even complete loss of existing
features—bony plates and pelvic spines.

The researchers have made several reasonable suggestions as to why the selection
pressure should be so strong, i.e. favouring the fast loss of spines and plates
in freshwater habitat:

As a trade-off for the bulky armour, sticklebacks likely gain in speed and agility,
so as lakes typically have places to hide, the fish can escape from any larger predators
lurking, assuming the sticklebacks can dart into ‘hiding holes’ quickly
enough.2

As many lakes lack the large predatory fish typical of ocean waters, the selection
pressure for armour no longer applies, hence fish lacking pelvic spines and/or with
less bony plate covering survive. Also, because fresh water lacks the rich calcium
reserves of sea water, bony armour could be “too costly to make”.2
Supporting this, biologists have documented that sticklebacks with reduced armour
are significantly larger in size. One of the researchers explained, “If the
fish aren’t expending resources growing bones—which may be significantly
more difficult in fresh water due to its lack of ions—they can devote more
energy to increasing biomass. This in turn allows them to breed earlier and improves
over-winter survival rate.”12

On the lake bottom, in the absence of a threat from larger predators, pelvic spines
not only lose their defensive value, but turn out to be a handicap when dragonfly
larvae and other bottom-dwelling predator larvae are present. University of Utah
biologist Michael Shapiro explained, “[D]ragonfly larvae can grab sticklebacks
by the [belly] spines, reel them in and eat them. They wait for sticklebacks to
swim by and grab them.”13,14

A decline in armour in stickleback populations has also been reported in other freshwater
locations.

For example, when researchers relocated 200 marine sticklebacks to freshwater ponds
on the University of British Columbia’s Vancouver campus, they soon observed
in the offspring that “natural selection favours reduced armour in freshwater”.12
From that and other studies, geneticists have now identified that a mutated genetic
switch is responsible for the loss of armour. Specifically, it affects expression
of the Pitx gene. In the pelvic region, the corrupted genetic switch prevents
spines forming in that area. Elsewhere, it can affect “a whole suite of bony
characters”2 not just the external bony plates but also jaw shape
and bones associated with protecting the gills.

Hence this now gives us a better understanding of genetic factors undergirding the
great morphological variation in freshwater sticklebacks,7 even such
differences as jaw shape, upon which natural selection can act. (Note that studies
have found that the genetic basis for low-platedness is present in populations of
ocean-going sticklebacks, albeit at low frequencies.)15

Note that at root here is brokenness or corruption—right
in line with the Bible’s account of the Creation being corrupted,
in “bondage to decay” (Romans 8:19–22). It is certainly no support for fish-to-philosopher
evolution, as there is no new genetic information here, rather the mutated (i.e.
broken) genetic switch simply prevents expression of a gene.

Despite Coyne and other evolutionists recognizing this, they are not backing away
from their belief in evolution. Prominent evolutionist Sean Carroll (with two colleagues),
writing in Scientific American of the stickleback’s disappearing
pelvic spine under the heading “A Beneficial Loss”
(emphasis added), nevertheless claims it “offers another vivid example of
adaptation through the evolution of a gene-regulating enhancer sequence.”17

Similar pro-evolution “spin” on the pelvic spine loss comes from Neil
Shubin and Randall Dahn, writing in Nature: “Surprisingly, some of
the most significant novelties in the history of life are associated not with the
evolution of new structures but with the loss or reduction of primitive ones.”18 Incredibly, they (and other
evolutionists)17,19 refer
to the stickback’s pelvic spine as being a limb, and therefore the observed
“limb reduction” in freshwater stickleback populations can be equated
with “hindlimb loss” in whales and manatees!20 (Whales and manatees, aquatic mammals, are presumed
over tens of millions of years of supposed earth history to have evolved from terrestrial
quadrupeds. However, as we have written previously (see, e.g.,
Not at all like a whale), such creative storytelling (with, of necessity,
it’s ever-changing storyline to fit each new discovery of contradicting evidence)
is completely without credible foundation.)

“Slow-and-gradual” notions debunked

An article in Science journal explained, “Since the 1930s, the prevailing
view has been that evolution moves in a slow shuffle, advancing in small increments,
propelled by numerous, minor genetic changes.”2 However, by evolutionists’
own admission, the stickleback findings represent a challenge to that view.

As we’ve seen, dramatic changes in the fish’s bony armour were traced
to an already-existing corrupted form of just one gene switch. The article
in Science conceded, “from an evolutionary perspective, this gene
may change at lightning speeds.”2 While evolutionists are describing
this as “rapid evolution”, the reality, in their own words, is simply
that “natural selection had taken its toll on the armored fish in just a few
years”.2

As The Scientist put it, “when these marine fish move to a new freshwater
environment, the low-plated phenotype has a selective advantage, and the low-plated
fish can appear quickly through natural selection at a higher
frequency of the preexisting genetic change.”21 (Emphasis added.)

Of course, this is right in line with a biblical perspective. (See
Brisk biters—fast changes in mosquitoes astonish evolutionists, but delight
creationists.) It’s most certainly not “rapid evolution”
at work as there is nowhere in evidence any sort of processes that might
have been able to change pond scum into people over billions of years. Rather, it
is just natural selection operating on existing genetic information, acting to favour
a corrupted gene switch,22
which thus becomes predominant in the stickleback population after just a few generations.
Such rapid changes within the stickleback ought be no surprise.

Rapid reversal, too! (and it’s not evolution, either)

Despite the lessons evolutionary researchers learned from having observed rapid
changes in saltwater sticklebacks colonizing freshwater lakes, they were in for
another stickleback surprise. The ScienceDaily headline summed it up, “Rapid,
dramatic ‘reverse evolution’ documented in tiny fish species”.
The article went on to explain that “Evolution is supposed to inch forward
over eons,” but in Lake Washington (near Seattle), stickleback
researchers had observed that “the process can go in relative warp-speed
reverse”.23
(Emphasis added.)

Other reports used similar language. “While evolution is usually expected
to creep along over eons, the stickleback has managed to evolve
in full-speed reverse … ”, explained a newspaper article,
citing it as “a rare example of animal reverting to an earlier evolutionary
version to survive a rapid change in its environment.”24 That report quoted one researcher as saying, “It
was very surprising.”

We see natural selection for sure, but no evidence of any new genetic information
of the sort needed to turn sticklebacks into scientists, whether over a short time
or long

So what actually happened? Five decades ago, when Lake Washington was so
polluted that visibility was limited to about 75 cm (30 inches), only about 6% of
the lake’s sticklebacks were fully plated (like the saltwater form)—the
remainder having little or no armour. But since a pollution cleanup operation began
in the mid-1960s, the researchers, “to their surprise”,24
recorded that the proportion of fully-plated sticklebacks (i.e. from snout-to-tail)
has increased to about 49% today, with an additional 35% having at least half of
their bodies shielded in bony armour.

The researchers surmise that prior to the cleanup, the murky water provided sticklebacks
with “an opaque blanket of security” against their primary predator
in Lake Washington, cutthroat trout, so armour plating was of little advantage.
But as visibility improved—by the early 1970s it was up to 3 metres (10 ft);
today water clarity is approaching 7.5 metres (25 ft)—low-armour sticklebacks
became more vulnerable to the cutthroat trout that suddenly could now see, and eat,
them.

Of course, this has nothing to do with microbes-to-man evolution, ‘reverse’
or otherwise. It is simply yet another example of natural selection operating on
existing genetic information—note that just prior to the cleanup, a small
proportion (6%) of the stickleback population were fully-plated. With increased
water transparency, there was now a stronger selection pressure against low-plating,
and so natural selection favoured fish with more armour. In the researchers’
own words summing up their paper in Current Biology (when we look past
their claims of “reverse evolution” and “rapid evolution”),
we see natural selection for sure, but no evidence of any new genetic information
of the sort needed to turn sticklebacks into scientists, whether over a short time
or long:

“On the basis of our genetic studies and simulations, we propose that the
most likely cause of reverse evolution is increased selection for the completely
plated morph, which we suggest could result from higher levels of trout
predation after a sudden increase in water transparency during the early 1970s.
Rapid evolution was facilitated by the existence of standing allelic variation
in Ectodysplasin (Eda), the gene that underlies the major plate-morph
locus. The Lake Washington stickleback thus provides a novel example of reverse
evolution, which is probably caused by a change in allele frequency
at the major plate locus in response to a changing predation regime.”25 (Emphasis
added.)

At the end of five decades of supposed ‘rapid, reverse evolution’, Lake
Washington’s stickleback population is still a population of sticklebacks.

This is not the first time that evolutionists have tried to claim shifting gene
frequencies in a population as evidence for molecules-to-man evolution—see
Goodbye, peppered moths
and Don’t fall
for the bait and switch. At the end of five decades of supposed “rapid,
reverse evolution”, Lake Washington’s stickleback population is still
a population of sticklebacks. No evolution has taken place.

Stickleback speciation is not evolution

As mentioned at the start of this article, Nature journal has this year
decreed the stickleback to be one of “15 Evolutionary Gems”. (There
were five “Gems from the Fossil Record”, four “Gems from Molecular
Processes” with the stickleback being one of six “Gems from Habitats”;
specifically tagged: “Natural selection in speciation”.)4
The journal cited its own 2004 paper by the University of Wisconsin’s Jeffrey
McKinnon and his colleagues reporting that reproductive isolation in sticklebacks
“can evolve as a by-product of selection on body size”.26

Put simply, the basis for the claim that this is evidence of evolution can be summed
up as follows:

Individual sticklebacks tend to mate with individuals like themselves, i.e. of similar
size and occupying similar ecological niche.27
E.g. the long and heavy-bodied benthic form (feeds on invertebrates at the lake
bottom; has a relatively horizontal jaw and small eyes) usually prefers not to mate
with the shorter, slimmer limnetic form (sticklebacks that live in the surface waters
of lakes, feeding on plankton; they can have an upturned jaw and large eyes). Thus
the different forms can be said to be reproductively isolated.

Having demonstrated that forms with distinctively different physical features are
also reproductively isolated from each other, biologists can declare the
different forms to be different species, i.e. there has been speciation.

In sticklebacks, although the benthic and limnetic forms in the wild are reproductively
isolated, and therefore can technically be declared to be separate species, they
can still mate with each other. E.g. benthic and limnetic sticklebacks in Lake Enos
on Vancouver Island are now known to be interbreeding and are no longer two distinct
species.28 And of course,
as already mentioned, freshwater sticklebacks can be readily crossed with ocean-going
sticklebacks—in fact, it was through careful observation of such crosses that
the Pitx gene was identified.

Conclusion

The stickleback provides us with great examples of natural selection, mutations,
rapid adaptation and speciation. Claims that these are evidence for evolution are
completely without foundation. The observed changes in stickleback populations today
are in no way the sorts of changes needed to have changed fish into philosophers—ever.

I.e. they are anadromous, going from the sea up rivers to
spawn (as opposed to catadromous fish which go down rivers to the ocean to spawn).
Return to text.

Gibson, G., The synthesis and evolution of a supermodel,
Science 307(5717):1890–1891, 2005. Return
to text.

For example, sticklebacks in deep lakes typically feed in
the surface waters (on plankton) and frequently have large eyes, an upturned jaw
and short, slim bodies. In shallow lakes, however, sticklebacks are primarily bottom-feeders
with smaller eyes, a relatively horizontal jaw, and long, heavier bodies.
Return to text.

At the end of the extracted text was a reference to: Pennisi,
E., Nature steers a predictable course, Science 287(5451):207–209,
14 January 2000. Return to text.

Not surprisingly, the news media duly relayed the idea to
the general public. One hopes that thinking people might have had cause to see the
vacuity in statements like this from the BBC News: “Limb loss is implicated
in a number of big steps in evolution.” Rincon, P., Genome reveals limb number
recipe, BBC News, <http://news.bbc.co.uk/2/hi/science/nature/3625235.stm>,
14 April 2004. Return to text.

Lovinger, S., Eda controls stickleback armor—Finding
reinforces idea that small genetic changes control widespread and major evolution,
News from The Scientist 6(1):20050328-01, <www.biomedcentral.com/news/20050328/01>,
28 March 2005. Return to text.

More recent research has revealed that loss of armour can
be traced to different genes, not just one as first thought. Shapiro, M., Summers,
B., Balabhadra, S., Aldenhoven, J., Miller, A., Cunningham, C., Bell, M., Kingsley,
D., Current Biology 19(13):1140–1145, 14 July 2009;
also: Different genes cause loss of body parts—pelvis and body armor—in
similar fish, ScienceDaily, <http://www.sciencedaily.com/releases/2009/06/090604124021.htm>,
5 June 2009. Return to text.

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Comments closed

A reader’s comment

Richard S.,United States, 6 December 2011

This article is very interesting in that it clarifies the reality of why changes have been and can be observed in stickleback morphology.

The whole notion of evolution from the simple to the complex demands that new information be somehow generated from nothing by blind chance.

The article makes it very clear that any observed changes are based on the survival of the fittest. Of course, the fittest ALWAYS survive the best!

What is overlooked by many evolutionist folks is the fact that Life is NOT based only on any special recipe of chemicals and mild environmental temperatures.

Rather, All of Life is based on special coded information that directs the constitution of the chemical recipe and how and when it is to be assembled into whatever life form is indicated.

I keep asking for even one single example of a true code that demonstrably has NO author, but only blind chance assembly.

Just as the old alchemists were unable to stew up some gold from cheaper stuff, scientists today will remain unable to stew up any living cells without the prerequisite code. No cutting and pasting of any existing code allowed!